Japan is considering boosting the stockpile of the antiviral drug Avigan to three times the current amount for use in treating 2 million people infected with the new coronavirus, sources with knowledge of the matter said Saturday.

The drug, developed by a group firm of Fujifilm Holdings has been stored in Japan as a treatment for influenza. But it is seen as also effective in treating the COVID-19 pneumonia caused by the virus.

Since the drug is feared to cause birth defects, it cannot be used on expectant mothers or women who might get pregnant. Therefore, the homegrown drug has never been sold on the market and the stockpile has been managed by the government as a precaution for the outbreak of an influenza with which most people are not immunized.

Fujifilm Toyama Chemical Co. began clinical tests to evaluate the efficacy of the drug, also known as Favipiravir, to COVID-19 patients on Tuesday. If such an efficacy is confirmed, the government might approve the drug for use in COVID-19 treatment this summer.

Avigan calls for different dosages in the treatments of the coronavirus and the influenza.

The current stockpile is enough to treat 700,000 people if used as an anti-coronavirus drug, and 2 million people as an anti-flu drug.

Fujifilm Holdings has been asked by the government to increase the output of the drug. Since the drug has been increasingly sought by foreign governments as the coronavirus pandemic spreads, the Japanese company is also considering outsourcing the production, the sources said.